Excerpts from Paul Mackerras's message of February 10, 2021 11:28 am: > On Mon, Jan 18, 2021 at 04:28:07PM +1000, Nicholas Piggin wrote: >> The slbmte instruction is legal in radix mode, including radix guest >> mode. This means radix guests can load the SLB with arbitrary data. >> >> KVM host does not clear the SLB when exiting a guest if it was a >> radix guest, which would allow a rogue radix guest to use the SLB as >> a side channel to communicate with other guests. > > No, because the code currently clears the SLB when entering a radix > guest, Not AFAIKS. > which you remove in the next patch. The next patch avoids clearing host SLB entries when a hash guest is entered from a radix host, it doesn't apply to radix guests. Not sure where the changelog for it went but it should have "HPT guests" in the title at least, I guess. > I'm OK with moving the SLB > clearing from guest entry to guest exit, I guess, but I don't see that > you are in fact fixing anything by doing so. I can set slb entries in a radix guest in simulator and observe they stay around over host<->guest transitions, and they don't after this patch. Thanks, Nick
